This invention relates generally to airfoil structures, and, more particularly, to all-moving airfoil structures having vortex generating devices for facilitating control of the airfoil.
Modern jet aircraft frequently employ all-moving horizontal stabilizers wherein the entire horizontal stabilizer may be deflected to control the ascent or descent of the aircraft. An elevator is typically hinged to the stabilizer and faired into its trailing edge to provide further control in a like manner. In addition, the elevator may have one or more elevator trim tabs on its trailing edge.
The stabilizer is typically mounted on a trunion shaft which extends laterally into the stabilizer from the aircraft fuselage, or, in the case of a T-tail aircraft assembly, from the aircraft fin. Deflection of the stabilizer is effected by rotating the trunion shaft. A hydraulic actuator is positioned inside the aircraft fuselage or fin for this purpose.
The elevator is typically mechanically linked to the stabilizer and the stabilizer trunion shaft such that a deflection of the stabilizer in either direction causes a proportional deflection of the elevator in the same direction about its hinge axis. Thus, the single hydraulic actuator within the fuselage or fin drives both the stabilizer and its associated elevator.
In practice, it is found that large moments are required to vary and maintain the deflection of the stabilizer and its elevator during flight, with the required moments being highest when the stabilizer is in a position of maximum deflection. Thus, large and heavy hydraulic actuators are necessarily employed. Since these actuators are located in a part of the plane where weight and size characteristics are particularly critical, they impose certain structural and design limitations upon the tail assembly of the aircraft. For some time it has been recognized that smaller and lighter actuators could be used if a way could be found to reduce the moments exerted about the elevator hinge and stabilizer trunion shaft when the stabilizer is deflected at high angles of attack.
It has been recognized that the large moments are due to rearward displacement of the center of pressure as the stabilizer is deflected, with the center of pressure moving to a maximum rearward position near the center of the elevator as the stabilizer is deflected to a high angle of attack. Thus, a device which reduces the rearward displacement of the center of pressure as the stabilizer is deflected has been sought as a way to reduce the moments about the elevator hinge axis and the stabilizer trunion shaft.
Accordingly, it is the general object of the present invention to provide an all-moving airfoil which requires a relatively smaller moment to vary and maintain its angle of attack.
More particularly, it is an object of the present invention to provide a device which reduces the moments about the elevator hinge and the stabilizer trunion shaft of an airplane all-moving horizontal stabilizer.
It is also an object of the present invention to provide a device which reduces the rearward displacement of the center of pressure on an all-moving stabilizer as the stabilizer is deflected.
It is a further object of this invention to provide a device which accomplishes the foregoing objects and which may be retrofitted onto all-moving horizontal stabilizers of existing airplanes.